The Full Displacement Pile Tip (FDPT) is a drilling bit that is very effective in penetrating many types of soil in order to install a steel pier for building foundation support. The FDPT is so efficient in laterally displacing soil that the concrete required to supplement the installation is minimal and soil waste is minimal. This speeds up construction at reduced costs.
Support is crucial in the construction of a building. Where soil is loose or cannot be adequately compressed to support the building, then deep holes are drilled under the foundation and concrete is typically poured into holes for reinforcement. Further, where hardened bedrock is located beneath the building, then a very sturdy bit is required to penetrate the rock as an anchor.
There have been several improvements in the conventional installation of concrete foundation piles or piers. Cutting tips permit the piers to be installed in a single operation, rather than involving installation by vibration of the ground. Cutting tips minimize the need for pre-drilling a location. The entire pier is rotated as it is drilled into the ground. However, this tends to loosen the soil and actually reduces support. Additionally, different soil compositions and hole depths create challenges for these drilling tools.
To address the concerns of soil loosening, devices such as a hollow stem auger with a tapered shaft to allow for simultaneous injection of concrete with a full displacement body are sometimes used. These augers have outward flights over a tapered section so as to compact the surrounding soils. Auger pressure grouting with displacement provides advantages because injecting the grout under pressure creates relatively high bearing capacities, promotes relatively fast construction, and lateral displacement of the soil minimizes spoilage disposal since compacting the soil laterally tends to improve the soil strength. Lateral displacement is achieved by auger bits with tapered stems, which tend to force the displaced soil laterally outward. Operations utilizing these methods must extend to considerable depths, making wear-resistance an important feature of bit design. An example is shown in U.S. Pat. No. 7,198,434, which discloses an auger bit with anti-wear protrusions that traps soil in protective positions on the stem and flighting for protection from wear. However, this device and method require auger extraction when pumping grouting material. Extraction involves additional time and creates some spoilage.
Another method involves a detachable end plate on the design tip depth, with injection of concrete. The soil is first displaced laterally around the pier. Then, upon reaching the design tip depth, a center bar is placed inside the drill stem and filled to a level above ground with concrete. During extraction, the left-handed flight above the displacement body picks up any caved material and re-compacts it back into the soil. The soil is prevented from decompressing by the pressure from the displacement body, in addition to the hydrostatic pressure from the concrete in the stem. The disadvantage is again time because several steps are involved, including drilling, and then center bar installation prior to concrete pumping.
Piers can also be installed using high torque hydraulic drilling rigs which rotate a specialized displacement tool into the ground, causing the ground to be compacted. Although, these processes provide deep foundation support and eliminate some of the high costs and delays related to disposing of contaminated soil, flights are required to go all the way up the drill shaft for displacement purposes. Having flights all along the shaft increases spoilage. Moreover, these methods require concrete to be poured immediately.
Another remedy for the lack of support of the pier is to inject grout around the pier to fill up the space caused by loosened soil. This too presents support problems because it is difficult to inject grout in a uniform and controlled manner and may even overly compress the surrounding soil. One known method involves displacing soil outwardly and then simultaneously filling the resulting void with grout around the pier. Though this device solves part of the problem by increasing productivity, it also requires immediate injection of grout, causes spoilage, and does not account for tougher drilling projects which require a sturdier drill tip.
To avoid concrete injection, an advance in driving and drilling systems where the drill tip must be retrieved from the drilling site after drilling is complete is shown in U.S. Pat. No. 7,914,236, which discloses a tubular shaft with two cylindrical sections and a helical flight attached to an exterior surface of the tapered portion. But, the problem with the flat surface perpendicular to the centerline of the tubular pile, is that the flat surface generates heat. When heat is generated at the pile tip it begins to melt the tip, which may cause the whole pier to collapse or worse, to grossly deform the surrounding soil resulting in potential future problems.
Another device for an improved drill tip involves a pier attachment structure with a diameter no greater than the width of the pier and a soil penetrating body having a plurality of circular stepped flights forming the shape of a descending continuous conic spiral organized around a center axis. However, this conical spiral at the tip meets a flat bottom at the base, which also generates too much heat.
The problem with all of the foregoing drill tips is that they need to be replaced as they get worn down from frequent bearing into hard soil with high rock content and/or they require concrete pumping to correct for deficiencies. Multiple steps in the drilling and installation of piers increase costs, result in delays, require heavier drilling rigs, and impose an obligation to remove and transport the extracted soil.
Currently the methods for improving drill tips without concrete injection, focus on the power of the drilling rig to force the shaft into the hole and have not sufficiently increased the durability of the drill tip. Therefore, there is a need to improve the strength of the drill tip to allow higher penetration in firm soil and to allow smaller and less expensive drilling rigs to accomplish the task. Less wear points also will decrease the amount of heat generated at the tip to prevent melting. My invention solves these problems by creating a device which comprises a conical shape to reduce heat, more steel at the cutting edges to abate wear—specifically, at least four flanges or “fish-tails” at the cutting edges—and tapered flights with thickened steel to improve cutting and minimize spoilage. The drill tip is actually left in the ground with the pier, so minimal concrete is required, and there is no extraction creating spoilage.
Further, my device has self-aligning capabilities. This is important because the tip is very heavy, so features which facilitate manual handling of the drill tip improve operations by saving time.